ABSTRACT

Base shear and sloshing response control in ground-supported circular cylindrical liquid storage tank is achieved by oblate spheroid base isolation (OSBI) system used along with floating surface diaphragm on the contained liquid. The new base isolation system, OSBI proposed herein is based on rolling-friction mechanism in ellipsoidal-shaped isolators in both the horizontal axes. The surface diaphragm is proposed to float on the free liquid surface to control the sloshing amplitude. The tank is analyzed using the coupled acoustic-structural (CAS) approach in finite element method (FEM). In order to have conformity of the present FE model, the FEM results are compared with the mechanical lumped-mass model of the tank (without surface diaphragm). The seismic response is investigated for the tank subjected to harmonic and real-earthquake excitations. The parameters considered for the analysis are the aspect ratio of the tank, eccentricity of the isolator, and thickness of the diaphragm. The seismic response quantities evaluated are base shear, sloshing displacement, and impulsive hydrodynamic pressure in the tank. Further, to study the effectiveness of the OSBI, the seismic responses of the tank subjected tri-directional components are compared with the two horizontal bi-directional components of the earthquakes. Also, the sloshing displacement with and without surface diaphragm in the non-isolated and base-isolated tanks are compared. From the results, it is observed that the OSBI system is efficient in mitigating the seismic responses in the tanks and the surface diaphragm is efficient in controlling the sloshing displacement. The superior performance of the proposed isolator depends on the design parameters, namely, eccentricity, and coefficient of rolling friction selected. The effectiveness of the surface diaphragm depends on the choice of material and thickness adopted.

摘要

地面支撑的圆柱形储液罐的底部剪切和晃动响应控制是通过与所装液体上的浮动表面隔膜一起使用的扁球体底部隔离（OSBI）系统实现的。本文提出的新型基础隔振系统 OSBI 基于椭圆形隔振器在两个水平轴上的滚动摩擦机制。建议将表面膜片漂浮在自由液面上以控制晃荡幅度。使用有限元法 (FEM) 中的耦合声-结构 (CAS) 方法对储罐进行分析。为了符合目前的有限元模型，将有限元结果与储罐的机械集总质量模型（无表面隔膜）进行了比较。研究了经受谐波和真实地震激励的储罐的地震响应。分析时考虑的参数是罐的纵横比、隔振器的偏心距和隔膜的厚度。评估的地震响应量是储罐中的基础剪切、晃动位移和冲击流体动力压力。此外，为了研究 OSBI 的有效性，将受三向分量影响的储罐的地震响应与地震的两个水平双向分量进行了比较。此外，比较了非隔震罐和基础隔震罐有无表面隔板的晃荡位移。从结果中可以看出，OSBI 系统在减轻储罐中的地震响应方面是有效的，而表面隔板在控制晃荡位移方面是有效的。所提出的隔振器的优越性能取决于设计参数，即偏心率和选择的滚动摩擦系数。表面膜片的有效性取决于所采用的材料和厚度的选择。